The present disclosure relates to a magnetic coupling element magnetically coupled to another magnetic coupling element, a foreign substance or the like, a device (magnetic coupling device) and a system (magnetic coupling system) which use the magnetic coupling element.
Particularly, the disclosure relates to a detection device detecting a mixture of the foreign substance (such as a metal, magnetic material, and magnet) heated by a magnetic flux between a non-contact power supply device and an electronic device which configure a non-contact power supply system, a power reception device, a power transmission device and the non-contact power supply system.
In recent years, a power supply system (called as a non-contact power supply system or a non-contact power transmission system) performing the power supply (power transmission) in a non-contact manner with respect to a consumer electronic (CE) device (electronic device for a consumer use) such as a mobile phone and a portable music player, for example has attracted much attention. Accordingly, a power charge can be started by simply putting the electronic device (secondary device) on a charge tray (primary side device) instead of plugging (connecting) a connector of the power supply device such as AC adapter to the CE device. As a result, a terminal connection between the electronic device and the charging tray is not necessary.
In this way, as a method of supplying the power in the non-contact manner, an electromagnetic induction method has been well known. In addition, in recent years, a non-contact power supply system adopting a method which is called a magnetic field resonance method using a resonance phenomenon has attracted attention.
The non-contact power supply system using the magnetic field resonance method has an advantage in that the power can be transmitted between devices which are located further far away from each other compared to the electromagnetic induction method. In addition, even if an alignment between the power supply source (power transmission coil) and a power supply destination (power reception coil) is a little poor, there is an advantage in that transmission efficiency (power supply efficiency) is not lowered too much. However, it is unchanged in that any one of the magnetic field resonance method and the electromagnetic induction method adopts the non-contact power supply system (magnetic coupling system) using the magnetic coupling between the power supply source (power transmission coil; magnetic coupling element) and the power supply destination (power reception coil; magnetic coupling system).
Incidentally, one of the important factors in the non-contact power supply system is a countermeasure against the heat generation of the foreign substance such as a metal, magnetic material, and magnet which generate heat due to the magnetic flux. When supplying the power in the non-contact manner without being limited to the electromagnetic induction method or the magnetic field resonance method, if the foreign substance is mixed in a gap between the power transmission coil and the power reception coil, there is a possibility that the foreign substance may generate heat due to the magnetic flux the foreign substance. In addition, the heat generation of the foreign substance results from a current (eddy current, ring current, circular current) produced in the foreign substance metal by passing through magnetic flux to a magnetic loss (hysteresis loss) occurring in a foreign substance magnetic material or a foreign substance magnet due to the magnetic flus passing through the foreign substance, the foreign substance magnetic material or the foreign substance magnet.
As a countermeasure against the heat generation, there have been proposed many methods which detect the foreign substance by adding a foreign substance detection system to the non-contact power supply system. For example, a method using an optical sensor or a temperature sensor has been known. However, the method using the sensor results in increased costs in a case of a wide power supply range as in the magnetic field resonance method. In addition, for example, according to the temperature sensor, since the output result on the temperature sensor depends on a thermal conductivity around the sensor, the design constraints are also imposed on the devices of a power transmission side and a power reception side.
Therefore, by focusing a change in parameters (current, voltage, and the like) when a foreign substance metal enters between the power transmission side and the power reception side, a method of determining whether or not the foreign substance is present has been proposed. According to such a method, since there is no reason to impose any design constraint or the like, it may be possible to reduce the cost.
For example, Japanese Unexamined Patent Application Publication No. 2008-206231 discloses a method of detecting the foreign substance metal using a modulation degree (change in an amplitude and phase) during a communication between the power transmission side and the power reception side, and Japanese Unexamined Patent Application Publication No. 2001-275280 discloses a method of detecting (foreign substance detection using a DC-DC efficiency) the foreign substance metal using an eddy current loss.
However, the methods proposed in Japanese Unexamined Patent Application Publication Nos. 2008-206231 and 2001-275280 do not take into account an influence due to a metal housing of the power reception side. When considering the power charge to a general-purpose portable device, there is a high possibility that any type of metals (metal housing, metal components, or the like) may be used in the portable device. Therefore, it is difficult to identify a change in parameters resulting from the “influence due to the metal housing”, or otherwise from “mixing of the foreign substance metal”. If Japanese Unexamined Patent Application Publication No 2001-275280 exemplified as one example, it is not possible to identify whether the eddy current loss occurs in the metal housing or otherwise occurs due to the foreign substance metal mixed between the power transmission side and the power reception side. In this way, it is to be understood that the techniques proposed in Japanese Unexamined Patent Application Publication Nos. 2008-206231 and 2001-275280 are unable to accurately detect the foreign substance metal.